在猪加入时出现投射错误
问题描述：
我有一个执行JOIN的脚本;当我在它成功的小数据运行它，但是当我增加数据的大小我得到这个错误：在猪加入时出现投射错误
14/10/07 19:10:19 ERROR executionengine.Launcher: Backend error message
org.apache.pig.backend.executionengine.ExecException: ERROR 0: Exception while executing [POProject (Name: Project[tuple][0] - scope-577 Operator Key: scope-577) children: null at []]: java.lang.ClassCastException: java.lang.Long cannot be cast to org.apache.pig.data.Tuple
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.getNext(PhysicalOperator.java:339)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POLocalRearrange.getNextTuple(POLocalRearrange.java:304)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POUnion.getNextTuple(POUnion.java:167)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.runPipeline(PigGenericMapBase.java:282)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:277)
at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigGenericMapBase.map(PigGenericMapBase.java:64)
at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:764)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:364)
at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
at org.apache.hadoop.mapred.Child.main(Child.java:249)
Caused by: java.lang.ClassCastException: java.lang.Long cannot be cast to org.apache.pig.data.Tuple
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POProject.getNextTuple(POProject.java:475)
at org.apache.pig.backend.hadoop.executionengine.physicalLayer.PhysicalOperator.getNext(PhysicalOperator.java:334)
... 13 more
我想，这个问题是不是由于错误输入，而其大小（数据集中等大小不在开发服务器上运行，但在更大的群集上运行）。
你能帮我理解错误的原因吗？
答
我的猜测是大数据集中有一行是Long值而不是元组。这是造成演员异常。发布您的猪脚本和一些示例行也很有帮助。